This invention relates to the structure of electrodes for use in vacuum-type circuit interrupters, and more particularly to the electrode structure of the self-acting magnetically-driving type.
Electrodes for use in a vacuum-type circuit interrupter are generally provided with a plurality of slots for controlling the flow of current through the electrodes. These slots act to establish a parallelly reciprocating loop-like current path extending substancially in a circumferential direction of the electrodes, and a magnetic field thereby produced is utilized to impel an arc for avoiding objectionable local fusion of the electrodes to improve the circuit interruption performance of the circuit interrupter.
In the electrodes for use in the vacuum-type circuit interrupter, their contact-making surface serves also as an arc-running surface so that an arc can be strongly impelled by a magnetically driving force as soon as such an arc is produced. More precisely, as disclosed in, for example, U.S. Pat. No. 3,764,764, each of a pair of electrodes has an outer peripheral arc-running surface protruding toward the corresponding arc-running surface of the other, and its central area is recessed relative to the arc-running surface so that the electrode can make contact at its arc-running surface with the arc-running surface of the other.
However, such a prior art electrode structure has been defective in that interruption of a large current gives rise to a shift of an arc toward and onto the central area of the electrodes resulting in impossibility of exhibiting the desired circuit interruption performance.